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Nutrients and Energy in Food

MacronutrientsMacronutrients

MicronutrientsMicronutrients

EnergyEnergy

MicronutrientsMicronutrients

NutrientsNutrients

– are need to effectively extract energy from theare need to effectively extract energy from the

macronutrients via catabolismmacronutrients via catabolism

MacronutrientsMacronutrients– Protein, Carbohydrate and LipidsProtein, Carbohydrate and Lipids

–Contain stored energyContain stored energy

Vitamins and Minerals Vitamins and Minerals

Energy ContentEnergy Content

Carbohydrate contain 16 kj/gramCarbohydrate contain 16 kj/gram

ProteinProtein contain 17 kj/gramcontain 17 kj/gram

Fat contains 37 kj/gramFat contains 37 kj/gram

Alcohol contains 29 kj/gramAlcohol contains 29 kj/gram

How is energy content of How is energy content of food measured?food measured?

– BombBomb calorimetercalorimeter Measures the energy released when theMeasures the energy released when the

food is burntfood is burnt.

This includes energy from indigestible foods as This includes energy from indigestible foods as

well as digestible food .well as digestible food . The energy content of this "fibre" must be The energy content of this "fibre" must be

subtracted from the bomb calorimeter subtracted from the bomb calorimeter

measurement.measurement.

Bomb CalorimeterBomb Calorimeter

Food Sample

Thermometer

Water

Ignition fuse

Bomb

Water Tank

Stirrer

The extraction of energy The extraction of energy from foodfrom food

Repackaging energy inRepackaging energy in ATPATP packetspackets

– Glucose = approx 100 ATPGlucose = approx 100 ATP

– But catabolism maximum yield is 38 But catabolism maximum yield is 38 ATP / glucoseATP / glucose

– as little as 0 ATP as inas little as 0 ATP as in Brown Adipose TissueBrown Adipose Tissue

The rest is lost as The rest is lost as heatheat

CatabolismCatabolism

Energy Needs of the Body

Total Kilojoule Requirements

• The average day can be dived into three stagesThe average day can be dived into three stages:

Rest,Rest, • Energy need for each stage Energy need for each stage are about:are about:

Rest, 2000kjRest, 2000kj

Work 3-4000kjWork 3-4000kj

Play 3-4000kjPlay 3-4000kj

• Over all per day = from 6000kj for total bed restOver all per day = from 6000kj for total bed rest

to 14,000 for a very active individualto 14,000 for a very active individual

• The need depend on body mass and sexThe need depend on body mass and sex

WorkWork and and PlayPlay

Basal Metabolism

– The energy needs of the body at The energy needs of the body at complete rest complete rest

• Is not really “Is not really “basalbasal” as it can ” as it can change due to: change due to: temperaturetemperature

and diet.and diet.

Used for all Internal energy needsUsed for all Internal energy needsRecycle tissueRecycle tissueImmunityImmunity

Body warmthBody warmthReduced by Tissue decreaseReduced by Tissue decrease

Measure of energy needs of the body

Indirect CalorimetryIndirect Calorimetrymeasuring the amount of measuring the amount of COCO22 breathed out breathed out .

People can have a respirometer People can have a respirometer attached while movingattached while moving

Whole body:Whole body:

people can be housed in a room people can be housed in a room

connected to connected to COCO22 monitors for air In and out monitors for air In and out

Which nutrients are used first for energy? Actually all macronutrients are

used for energy all the time.

Different material in different Different material in different tissues eg.:tissues eg.:

The brain needs glucoseThe brain needs glucose

Aerobic Muscles use fatAerobic Muscles use fat

The liver uses mainly excess proteinThe liver uses mainly excess protein.

• Ideal Body WeightIdeal Body Weight

Obese

Calculate Body Mass Index (BMI)

From % Body fat– Measured with

Skinfold thickness buoyancy Electrical conduction

Desire % Body FatDesire % Body Fat

Body Condition Female Male Unhealthy <15% <10% Lean 17-22% 10-15 Normal 22-25% 15-18% Above Average 25-29% 18-20% Over weight 29-35% 20-25% Obese 35+% 25+%

Dangers of Under and Over weight

Framington study– indicated obesity increased

chance of early death cardiovascular disease diabetes

Framington Study

From Kennel and Gordon 1974

Underweight

Framington study indicated underweight increased – chance of early death

– infectious disease

– cancer

Anorexia nervosa and bulimia nervosa

Energy Use In BodyEnergy Use In Body

Weight LossWeight Loss

DietingDieting

Fat distributionFat distribution

Effect of fat Effect of fat distribution typedistribution type

Andomorphs– More likely to suffer

cardiovascular disease Gynomorphs

– Less likely to suffer cardiovascular disease

Benefits of Obesity

Obese people do not get Obese people do not get osteoporosisosteoporosis.

This may be due to their higher insulin secretion reducing This may be due to their higher insulin secretion reducing

calcium lost in the urine. calcium lost in the urine.

Causes of Obesity

– Nurture versus Nature

Nurture Theories

• Eating to satisfy : Eating to satisfy :

• Boredom Boredom • Parents Parents

• Stress Stress

• CultureCulture

• Effect of ageEffect of age

• Ego Ego

Most obese adults were slim when youngMost obese adults were slim when young

Obesity may be caused by phycologyObesity may be caused by phycology

Nature Theories

Obesity caused by physiology Dieting does not help

Ageing

Muscle tone Muscle tone

Diet induced ThermogenesisDiet induced Thermogenesis

Glycogen storage Glycogen storage variationsvariations

Need large food intake to maintain Nitrogen BalanceNeed large food intake to maintain Nitrogen Balance

Benefits of Obesity

Obese people do not get Obese people do not get osteoporosisosteoporosis.

This may be due to their higher insulin secretion reducing This may be due to their higher insulin secretion reducing

calcium lost in the urine. calcium lost in the urine.

Causes of Obesity

– Nurture versus Nature

Why Dieting Doesn't WorkWhy Dieting Doesn't Work Reduced energy intake causes the Reduced energy intake causes the

body to adapt:body to adapt: lowers “basal metabolismlowers “basal metabolism””

burns up fatburns up fat

reduces energy using tissuereduces energy using tissue

– lean body mass lean body mass

When you go off the dietWhen you go off the diet

use less energyuse less energy

get fatter than beforeget fatter than before